1. Field of the Invention
The present invention relates to a key groups to be hunted in an incoming call communication system. More particularly, the invention relates to a method of concentrating key groups to be hunted among incoming call terminals, which is used in a data switching system performing packet switching, frame relay switching, ATM (asynchronous transfer mode) switching and so forth, and also relates to a switching system carrying out said method.
2. Description of the Related Art
The incoming call communication service using key groups to be hunted provided through a telephone switching system, a data switching system and so on, is a service that, in the switching system like the above, provides a key number for a plurality of subscriber terminals and if a call selects the key number, the call is made to connect with an arbitrary idle subscriber terminal among the plural subscriber terminals. This service has already been considerably popularized.
In the incoming call communication service using key groups to be hunted like this, it is desirous that concentration of slave terminals in key groups to be hunted (merely referred to as a slave terminal or slave terminals hereinafter) can be performed without canceling the counterpart communication link, and also that the state of use of slave terminals after concentration thereof can be notified to a master terminal in key groups to be hunted (referred to as master terminal hereinafter).
Heretofore, this kind of technology has been disclosed by Japanese Unexamined Patent Publication (KOKAI) No. 63-16743 entitled "Key Number Control System." This publication describes that if the master terminal of the key number terminal group is in communication, a terminating call side switching system selects an idle slave terminal from the terminal group having key number, thereby establishing a communication line therethrough.
Hitherto, in the incoming call communication service using key groups to be hunted provided through a packet switching system, communication via an identical slave terminal was fixed to that terminal during the time from establishment of a call to cancellation of the same, so that it was not possible to change terminals among a group of slave terminals. It was also not possible to notify the state of use of slave terminals to the master terminal.
So far, in the incoming call communication service using key groups to be hunted provided through the packet switching system, communication was performed with an identical slave terminal during the time from establishment of a call to cancellation of the same, so that terminal change among a group of slave terminals was not possible. It was impossible, therefore, to effectively make use of slave terminals in correspondence with the state of communication traffic. For instance, communication links at respective slave terminals are usually less used at midnight, thus being made use of ineffectively.
If, therefore, it is possible to concentrate certain slave terminals onto certain other terminals, it becomes possible to make use of the former terminals for other purposes and also to design advantageous ways of use of slave terminals as a whole. However, there has been no proposal thus far on how to carry out such slave terminal concentration. Further, in the case of carrying out the slave terminal concentration, it is desirous to notify the state of current use of slave terminals to the master terminal after completion of the concentration, but there has been no prior art teaching how to make such a notice to the master terminal.